1. Field of the Invention
The invention relates to methods for forming a germanium-based intermetallic thin film on a substrate. Specifically, the invention relates to a low temperature process for making germanium-based intermetallic thin films on a substrate.
2. Description of the Related Art
Thermal annealing and laser annealing are two generally applied techniques in making semiconductor thin films. Both thermal and laser annealing techniques are, however, associated with certain problems and disadvantages. For example, as a high temperature process, rapid thermal annealing may cause undesired diffusion into the surrounding material. In a laser annealing technique, the spot size of the laser is generally small, thus it is required to move the laser to different spots to anneal the entire area. During this process, some parts are missed while some parts are annealed multiple times, forming a “pattern”. These pattern effects may degrade the device performance. Although microwave (MW)-assisted synthesis is appealing as a much simpler, faster, extremely energy efficient and environmentally friendly process, the breadth of low temperature synthesis of alloy thin films using microwave radiation has not yet been explored.
In past two decades, copper germanide (Cu3Ge) has received widespread interest in the field of microelectronics [A. P. Peter, L. Carbonell, M. Schaekers, C. Adelmann, J. Meersschaut, A. Franquet, O. Richard, H. Bender, T. Zsolt, and S. van Elshocht, Intermetallics 34, 35 (2013)]. The use of Cu3Ge as a potential candidate for interconnections and contacts in Si and GaAs technology is due to its low contact resistivity and high thermal stability [L. Krusin-Elbaum and M. O. Aboelfotoh, Appl. Phys. Lett. 58, 1341 (1991); M. O. Aboelfotoh, C. L. Lin, and J. M. Woodall, Appl. Phys. Lett. 65, 3245 (1994)]. Erofeev et al. investigated the DC and RF performance of the gold free and fully Cu—Ge metalized GaAs pHEMT for high frequency application [E. V. Erofeev, V. A. Kagadei, and A. I. Kazimirov, 2011 International Siberian Conference on Control and Communications (SIBCON), Krasnoyarsk, Russia, 15-16 Sep. 2011, pp 261-264]. Cu3Ge is also a potential material for recording layers in write-once blue-ray discs [G. Guizetti, F. Marabelli, P. Pellegrino, A, Sassella, J Appl. Phys. 111, 043503 (2012)]. Furthermore, Cu3Ge is also a promising material for metallization of superconducting YBa2Cu3O7-x films [D. Kumar, R. D. Vispute, O. Aboelfotoh, S. Oktyabrysky, K. Jagannadham, and J. Narayan, J Electron Mater., 25 1760 (1996)]. Traditionally, high temperature anneals greater than 400° C. in a vacuum environment are required to synthesize Cu3Ge thin films, preventing their use in plastic-based, light-weight, and flexible substrates for thin film transistors, solar cells and light emitting diodes. In addition, the high temperature synthesis makes it difficult to be introduced into the resist lift-off technique. These drawbacks led to the motivation of developing a new synthetic method that can overcome these problems and facilitate product formation.
Needed in the art is a low-temperature process for making semiconductor thin films, e.g., germanium-based intermetallic thin films.